Mosaic electrode for television tubes



May 10, 1938. M. KNOLL 2,116,901

MOSAIC ELECTRODE FOR TELEVISION TUBES Filed Jan. 20, 1936 INVENTOR. AX KNOLL BY MW ATTORNEY.

Patented May 10, 1938' PATENT OFFICE MOSAIC ELECTRODE FOR TELEVISION TUBES Max Knoll, Berlin, Germany, assignor to Telefunken Gesellschaft fiirllrahtlose Telegraphic m. b. 11., Berlin, Germany, acorporation of Germany Application January 2o, 1936,8181 No. 59,888 In Germany November 30, 1934 a Claims.

The present invention is concerned with a further development of the electron miscroscope type of television transmitter or televisor disclosed in the patent application of Fritz Schroter,

, Serial 32,768, July 23. 1935, and it concerns,more

particularly speaking, a simplified form of construction of the surface of the screen plate comprised in the arrangement therein disclosed, together with changes in the assembly and mountlil ing of the system of the tube associated therewith.

The above mentioned patent application disclosed means for the scanning of the picture at the televisor or transmitter end (predicated upon II the use of cathode-rays) of the following kind: Upon a photo-electrically activated cathode, all or part of the picture to be transmitted is projected or imaged by the aid of an optical device. The photoelectric cathode, by the aid of an electron optical system is imaged upon a row of dots or a screen plate, the constituent elements of which consist of a plurality of insulated collector or absorber electrodes; To the said screen plate or grate, or the said row of dots are thus imparted charges corresponding, to the brightness values of the pictures, and these charges. by scanning with an independent cathode-ray pencil, are evaluated from the posterior face of the screen or grate surface for the purpose of transa mission.

The arrangements disclosed in the above mentioned patent application may be modified in this manner that the screen surface is scanned from the anterior side or face rather than posl teriorly. A schematic representation of a tube thus modified is illustrated in the single figure of the drawing.

The picture projected upon the photo-active layer i by the aid of an optical system 2 is thrown, by the agency of an electron-optic system 3, upon a grate or screen plate 4. The scanning of the surface of the said screen is accomplished from the same side by the agency of v a cathode-ray pencil which is generated and focussed in the system 1, while being deflected by the deflecting system 8 in the customary way. For the collection of the secondary electrons, in analogy with'the electrode I! mentioned in the 'co-pending patent application above referred to, there sew a reticulated electrode 9. In this mode of scanning, theconstruction of the screen surface may be simplifled'to an essential degree. Whereas the-construction of the meteor screen plate surface disclosed in the above mentioned ll patent application involvesa problem of precision caused to coalesce into tiny spherules, the latter (Cl. est-27.5) v

mechanics that is but hard to solve seeing the. e for the construction of the same is required a metallic electrode into which pins are inserted, each one of which is insulated in reference to the electrode, the screen elements according to 5 the present invention, by a method hereinafter to be disclosed and described in more detail, may be brought upon a thin coherent (unbroken) insulation layer or coat 5 which, upon the opposite face. is bounded by an unbroken conducting coat 8. 10 This corresponds eactly to the electrode 9 in the earlier patent application. ,Now, for the manuglass, upon which is thereupon dusted fine metallic powder in such measured quantities that, after the drying of the binder or cement, there 20 will remain sufllciently large insulating intervals or gaps. The metallic powder, if desired, could also be caused to sinter in upon or the insulation layer.

Another method to make grate or screen ele- 25 ments consists in that upon an. insulation coat is applied a thin and uniform film of metal, say, silver, whereupon the said metal coat is heated to the fusion point, with the result that the metalwon the insulating substratum or support is constituting the screen elements.

For the preparation of the een elements'there is suited also a,daguerreotype procedure. A metal plate consisting, e. g.,of aluminum, is provided by oxidation with a thin layer or film of insulation. On top of the latter is precipitated or deposited a tenuous film of metal and then exposed to the action of halogen vapors resulting in, forinstance, iodization. The-coat possessing photographically active or responsive properties which is thus made is thereupon exposed by means of a dotted screen known from theart of autotypy by a printing process, then developed and fixed so that at the exposed points there result tiny screen elements consisting of pure silver.

Another feasible process is to produce the screen elements upon the, insulating layer by means of metallimtion by the interposition of a pattern or templet. Upon the insulation layer is laid, for instance, a metallic networkor gauze @(reticulum) or else a grate obtained by an auto type process whose openings are equal to, or smaller than, the diameters of the elementary picture points or areas. The screen elements are ill obtained by reason of the fact that the pattern or stencil as well as'the subjacent insulation layer are exposed to the action oi. metallic vapors, say, inside a high vacuum or by way of cathode spatter or disintegration;

Having disclosed my invention, what is claimed is:

1. The steps and method of preparing a photo sensitive mosaic electrode upon a metallic plate electrode which comprise oxidizing one surface of the plate electrode, depositing upon the oxidized surface a. tenuous finely divided layer of metal,

photo-graphically sensitizing the produced layer of metal, projecting the light image of a multiapertured surface upon the photographically sensitized layer, and photographically developing and fixing the light exposed layer to produce thereupon minute isolated metallic elements supported upon the oxidized surface. I

2. The steps and method of preparing a photosensitive mosaic electrode upon a metallic plate electrode supported within an enclosing envelope which comprise oxidizing one surface of the plate electrode, depositing upon the oxidized surface a tenuous film of metal, exposing the deposited film to halogen vapors to produce on the odized surface a photographically sensitive film, directing a light image of a multi-apertured surface upon the photographically sensitized film, and photographically developing and fixing the light exposed film to produce thereupon minute isolated metallic elements supported upon the oxidized surface.

MAX KNOLL. 

